No, it is not a good visualization.

You cannot easily compare the same browser across two versions of jquery because each browser starts at a different point on the Y axis for each column; you cannot easily scan from one column to the next to see the difference but must jump back and forth figuring out start-end points and trying to guess at differences.

It makes it difficult to compare the individual speeds across different versions because the nature of the chart compresses the vertical space to make the larger of the two stacked bars fit into the graph, artificially compressing the Y axis (which measures the only thing we care about in this graph) and diminishing the scale for all of the items being compared.

The only thing it makes easy to see is an aggregate of browser speeds across versions (and since nothing runs on all browsers at the same time this measurement is not very valuable) and as a comparator of individual browsers against each other, which is the second least-important metric in these charts.

While it is possible to compare the same browser across two different version of jQuery, it's pretty difficult to do so: you need to manually "extract" the slivers from the two different bars and compare them visually, which is difficult and imprecise. I think it would be more useful to have one pair of bars for each browser (old vs. new jQuery version), and then a pair of bars for "total over all browsers" (old vs. new jQuery). That is slightly more verbose, but more useful too.